<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>这是字母逆序输出的代码</title>
</head>
<body>
<script>
  function reverseString(message){
    // wirte your code here
      return message.split('').reverse().join('');
  }
  document.write(reverseString('hello'));// should return 'olleh'

</script>
</body>
</html>